This invention relates to the identification of tools or tool chambers producing defective products in a multiple tool manufacturing environment where those tools are reused in successive stages of manufacture of a single product. More particularly, the present invention relates to computer implemented methods and systems for storing and analyzing product history and failure data to determine which tools produce defective products when reused in that manner.
FIG. 1A is a diagram 2 of a manufacturing process flow of processing steps employed in the manufacture of microelectronic devices comprising semiconductor chips. The diagram 2 illustrates a series of cycles of processing steps starting with a set of Front End Of Line (FEOL) block 3 of processing steps and continuing until the end of a set of Back End Of Line (BEOL) block 4 of processing steps. Below the FEOL block 3 and BEOL block 4 is a chart showing the metallization process phases from the metal layer phase 1, through to the last three metallization phases N−1, N and N+1. The semiconductor devices are formed in the FEOL process steps and then preferably consecutively metal layer 1, . . . metal layer N−1, metal layer N, and through N+1 are formed in the BEOL processing.
To simplify the description it is assumed that the processing occurs in several cycles of consecutive sequence processing steps which are repeated several times to form the metallization layers required on a semiconductor device. That is to say that several consecutive processing steps are performed repeatedly. The processing is performed at stages each of which includes several tools (hereinafter referring to both individual tools and chambers in multi-chamber tools). The various stages perform functions such as deposition of metal, deposition of dielectric layers, patterning (forming masks), and etching by a process such as Reactive Ion Etching (RIE). While the method of this invention does not require repetition of the processing sequence, the description included herein relates to repeated cycling through the same sequence of tool stages. It will be well understood by those skilled in the art that the sequence of processing and the tools employed may vary considerably, and that the present invention can be applied to such diverse sequences of operation as well.
In many cases in the manufacture of semiconductor devices, similar process steps are repeated several times during a product manufacturing cycle and a common set of tools is reused for each of such similar process steps. In order to enhance the yield of manufacturing of semiconductor devices, it is necessary to identify a bad tool or a tool that is under-performing, but also to identify the best performing tools. Furthermore it is desirable to determine which one of the chambers of a multi-chamber tool is bad, i.e. under-performing. It is also desirable to determine which ones of the tools (chambers) is one of the best performing units on factory floor. Heretofore the state of the art methods employed for detecting under-performing tools in manufacturing were based on uni-process analysis. A common method of analysis has been to monitor the yield for each process step individually and to identify the tool performance based upon that data. However in a very complex process where very large numbers of steps are performed without the ability of being able to monitor the yield for each process step, the problem of determining the level of performance of each individual tool has become a difficult problem.
Referring to FIG. 1B, a system 10 is shown for performing data collection from a series of workpieces W being manufactured on a factory floor 12 which includes a set of tools 12-1 to 12-4, a Data Collection Processor (DCP) 15 and a functional test apparatus 17. The sets of tool stages 12-1 to 12-4, which include a deposit metal stage 12-1, a deposit dielectric stage 12-2, a patterning stage 12-3 and an RIE stage 12-4. Each of those stages 12-1 to 12-4 may include two or more similar tools which can process a given workpiece W. The two or more similar tools at a single stage are provided so that when one or more tools at a stage is/are otherwise occupied with processing or in need of repair another available tool at that stage can process the workpiece W without delay. The workpieces W enter the deposit metal stage 12-1 on conveyor line 11A. After processing at deposit metal stage 12-1, workpiece W moves on conveyor line 11B to dielectric deposition stage 12-2. After processing at stage 12-2, workpiece W moves on conveyor line 11C to patterning stage 12-3. After processing at stage 12-3, workpiece W moves on conveyor line 17A to RIE stage 12-4 where three RIE tools A, B and C are shown to illustrate the fact that there can be several tools at a single stage. The RIE stage 12-4 includes RIE A tool RA, RIE B tool RB, and RIE C tool RC.
The identification of workpieces W processed by individual tools is supplied on lines 13-1 to 13-4 to the DCP 15. In particular, each of the tools in stage 12-1 is connected to send workpiece identification data on line 13-1 to the DCP 15. Each of the tools in stage 12-2 is connected to send workpiece identification data on line 13-2 to the DCP 15. Each of the tools in stage 12-3 is connected to send workpiece identification data on line 13-3 to the DCP 15. In stage 12-4 RIE A Tool RA is connected by line 13-4A to send workpiece identification data to line 13-4; RIE B Tool RB is connected to send workpiece identification data by line 13-4B to line 13-4; and RIE C Tool RC is connected by line 13-4C to line 13-4. Lines 13-4A to 13-4C are connected to line 13-4 to send the workpiece identification data workpiece identification data for the tools RA-RC to the DCP 15. There may also be some test data collected which is supplied to the DCP 15, but there is no overall test data supplied on lines 13-1 to 13-4 as to the effects of processing by each individual tool upon the overall quality of the workpiece W. There are other tests made by parametric testers at various stages in the process of manufacture that provide parametric yield data, as distinguished from functional yield test data provided by the functional test apparatus 17 at the end of processing.
After completion of the first cycle of processing by the four stages 12-1 to 12-4, the workpiece W is recycled along line 14A to the input line 11 to stage 12-1 and is processed there by whichever tool is available in stage 12-1. Then the process is repeated at stages 12-2 to 12-4 as described above. The workpiece W is recycled N times through stages 12-1 to 12-4 repeatedly for manufacture of the metal layers until all of the metal layers including the metal layer N+1 have been manufactured in accordance with FIG. 1A. Then the workpiece W leaves the factory floor 12 on conveyor line 14Z which delivers it for testing to the functional test apparatus 17 which performs tests after all processing has been completed, as will be well understood by those skilled in the art. The data collected by the functional test apparatus is sent to the DCP 15.
FIG. 1C is a schematic diagram which comprises a chronological representation of several series of cycles of repetition of consecutive metallization processing by the stages 12-1 to 12-4 on the factory floor 12 by providing a duplicate block for each cycle of repetition of N repetitive uses of a stage in the manufacture of workpieces W which are being manufactured and tested.
The stage 12-1 includes a set of duplicate blocks for processing including deposit metal cycle 1 block 12-1A, a deposit metal cycle 2 block 12-1B therebelow; as well as deposit metal cycle N−2 block 12-1×; deposit metal cycle N−1 block 12-1Y and deposit metal cycle N block 12-1Z therebelow.
The stage 12-2 includes another set of duplicate blocks including a deposit dielectric cycle 1 block 12-2A, a deposit dielectric cycle 2 block 12-2B therebelow; a deposit dielectric cycle 2 block 12-2B, as well as deposit dielectric cycle N−2 block 12-2X; deposit dielectric cycle N−1 block 12-2Y and deposit dielectric cycle N block 12-2Z therebelow.
The stage 12-3 includes still another set of duplicate blocks including a pattern cycle 1 block 12-3A, a pattern cycle 2 block 12-3B therebelow; a pattern cycle 2 block 12-3B, as well as pattern cycle N−2 block 12-3X; pattern cycle N−1 block 12-3Y and pattern cycle N block 12-2Z therebelow.
The stage 12-4 includes yet another set of duplicate blocks including an RIE cycle 1 block 12-2A, an RIE cycle 2 block 12-2B therebelow; an RIE cycle 3 block 12-2B, as well as an RIE cycle N−2 block 12-2X; an RIE cycle N−1 block 12-2Y and an RIE cycle N block 12-2Z therebelow.
At the end of the first cycle of processing in RIE stage 12-4 in FIG. 1C, the workpiece W is transported on conveyer line 14A for recycling to stage 12-1 as indicated by block 12-1B which represents the fact that the workpiece W is now in the process of being subjected to BEOL metal layer 2 processing and that it will be processed consecutively by tools in the four stages 12-1 to 12-4, but that at each stage it will very likely be processed by a different tool at each of those stages 12-1 to 12-4 from the tool employed in the first cycle because some of the tools will be busy with other workpieces, or otherwise unavailable at the time the workpiece W arrives on line 14A. In the second cycle the workpiece is processed consecutively at deposit metal stage 12-1B; deposit dielectric stage 12-2B; pattern cycle 12-3B and one of the tools RA-RB in RIE stage 12-4B.
At the end of the second cycle of processing in RIE stage 12-4 in FIG. 1C, the workpiece W is recycled back on conveyer line 14B to stage 12-1 for BEOL metal layer 3 processing (not shown for convenience of illustration) and that it will be processed by tools in the four stages 12-1 to 12-4, but that it may be processed by different tools at each of those stages 12-1 to 12-4 from those of the first and second cycles because some of the tools will be busy with other workpieces, or otherwise unavailable at the time the workpiece W arrives on line 14B. Then the workpiece W is processed consecutively at deposit metal stage 12-1; deposit dielectric stage 12-2; pattern cycle 12-3 and one of the tools RA-RB in RIE stage 12-4 and the dots below line 14B indicate that numerous cycles of processing are omitted for convenience of illustration.
At the end of a subsequent N−3 cycle of processing (not shown in FIG. 1C), in RIE stage 12-4 the workpiece W is recycled back on conveyer line 14W to stage 12-1 for BEOL metal layer N−2 processing as indicated by block 12-1X which represents the fact that the workpiece W is now in the process of being subjected to BEOL metal layer N−2 processing and that it will be processed consecutively by tools in the four stages 12-1 to 12-4, but that it will probably be processed by different tools at each of those stages 12-1 to 12-4 from those of the some of the previous cycles because some of the tools will be busy with other workpieces, or otherwise unavailable at the time the workpiece W arrives on line 14W. Then the workpiece W is processed consecutively at deposit metal stage 12-1X; deposit dielectric stage 12-2X; pattern cycle 12-3X and one of the tools RA-RB in RIE stage 12-4X.
At the end of the N−2 cycle of processing in FIG. 1C in RIE stage 12-4, the workpiece W is recycled back on production line 14X to stage 12-1 for BEOL metal layer N−1 processing as indicated by block 12-1Y which represents the fact that the workpiece W is now in the process of being subjected to BEOL metal layer N−1 processing and that it will be processed by tools in the four stages 12-1 to 12-4, but that it will probably be processed by different tools at each of those stages 12-1 to 12-4 from those of many of the previous cycles because some of the tools will be busy with other workpieces, or otherwise unavailable at the time the workpiece W arrives on line 14X. In the N−1 cycle the workpiece W is consecutively processed at deposit metal stage 12-1Y; deposit dielectric stage 12-2Y; pattern cycle 12-3Y and one of the tools RA-RB in RIE stage 12-4Y.
At the end of the N−1 cycle of processing in FIG. 1C in RIE stage 12-4, the workpiece W is recycled back on production line 14Y to stage 12-1 for BEOL metal layer N processing as indicated by block 12-1Z which represents the fact that the workpiece W is now in the process of being subjected to BEOL metal layer N processing and that it will be processed by tools in the four stages 12-1 to 12-4, but that it will probably be processed by different tools at each of those stages 12-1 to 12-4 from those of many of the previous cycles because some of the tools will be busy with other workpieces, or otherwise unavailable at the time the workpiece W arrives on line 14Y. In the N cycle the workpiece is consecutively processed at deposit metal stage 12-1Z; deposit dielectric stage 12-2Z; pattern cycle 12-3Z and one of the tools RA-RB in RIE stage 12-4Z.
At the end of the N cycle of processing in FIG. 1C in RIE stage 12-4, the workpiece W is exits the factory floor back on conveyor line 14Z which delivers it to the Functional Test Apparatus 17 for functional testing as described above.
Referring to FIG. 2 a chart is shown of a prior art type analysis of the yield of a process step after the repetition of a process on a set on two tools, tool A and tool B at one stage, where one of the two tools A and B is actually performing better than the other. With current methods, by examination of a single process step as shown in FIG. 2 one might conclude that the performance of tool B is worse than that of tool A since the data shown on the chart in FIG. 2 would indicate that to be the case. However the problem with that approach is that the result may be attributable to the fact that semiconductor wafers with lower yields may have been processed on tool A at all of the other process steps, except the step analyzed, and yet tool B would be assumed to be the worse tool, even though that may not have been factually correct.
Current methods of detecting under-performance are limited in that as follows:                i.) they do not account for effects arising from repeated usage of a set of tools in subsequent process steps, as they all relate to a single processing step without accounting for past history;        ii.) by looking at only one process step, the analysis does not account for effects caused at prior or subsequent use of a common tool set and could lead to incorrect judgments regarding tool performance;        iii.) small and marginal effects are not detectable;        iv.) the under-performance of tools which perform variably over time, with periods of acceptable performance interspersed with finite periods of under-performance, are not detectable.        